Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Food Science and Human Nutrition

First Advisor

Earl G. Hammond

Abstract

Various factors affecting the hydrolysis of fats and oils by oat lipase were examined. Variety, growth location and their interaction significantly affected the lipase activity of oats. Harvest of oats at early stages of development produced more lipase activity/unit weight than late harvest;Caryopses produced with an impact-type dehuller exhibited greater lipase activity than those produced by a wringer-type dehuller;The activity of oat lipase at 38 and 42°C was lower than that at 40°C;Addition of 0.004% ethanolamine into the water used to moisten the caryopses, increased the lipase activity, but higher concentrations were inhibitory;Attrition in a fluidized bed of oat caryopses suspended in air partly removed the lipase. The lipase-rich particles from the fluidized bed were further fractionated by sedimentation in hexane. Such lipase concentrates could be used to speed fat hydrolysis;During the hydrolysis of soybean oil with moist oat caryopses, the free fatty acid content of the internal oat lipid increased only slightly, but there was continuing metabolism of the oats lipids during the incubation that resulted in an increase in linoleate and linolenate and a decrease in oleate and palmitate;During the hydrolysis of oil, glycerol accumulates inside the caryopses. When whole caryopses were washed continuously with recirculating water, all the glycerol that could be recovered was recovered in the wash water within the first 6 h;Erucic acid was released from crambe oil at significantly slower rates than the other acyl groups. Beef tallow and lard were hydrolyzed to 73% and 70% although the tallow was very near its melting point at the maximum operating temperature of 40°C. The hydrolysis of corn oil was slower than soybean oil. The inhibitory action of the diglyceride fraction of corn oil seemed to account for this effect. About 90% hydrolysis was achieved with 50 and 25% tallow dilution in hexane. Only 20% hydrolysis was achieved with neat castor oil, but dilution with equal weights of a hexane:benzene mixture resulted into 50% hydrolysis;After 1 week in a lipase bioreactor inoculated with the spores of Clostridium sporogenes, no growth of the spores could be detected.

DOI

https://doi.org/10.31274/rtd-180813-12208

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Shantilal Parmar

Language

en

Proquest ID

AAI9311527

File Format

application/pdf

File Size

144 pages

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